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Du-Bro Tri-Star R/C Helicopter Build & Review
December 1975 RC Modeler

December 1975 R/C Modeler

December 1975 R/C Modeler - Airplanes and RocketsTable of Contents

These pages from vintage modeling magazines like Flying Aces, Air Trails, American Modeler, American Aircraft Modeler, Young Men, Flying Models, Model Airplane News, R/C Modeler, captured the era. All copyrights acknowledged.

Du−Bro was the first American company to produce a radio control helicopter kit - the Whirlybird 505. That was sometime around 1972 It was modeled after the way free flight helicopters were built an the engine and propeller sitting on top of the main rotor, using a free-wheeling rotor that turned in response to the counter torque of the engine. Fixed pitch rotor blades were controlled via a flybar assembly as was the case prior to the advent of flybarless rotor heads. Du-Bro's next helicopter was a much-improved and very popular Hughes 300, using a driven rotor with the engine mounted in the fuselage. It also used a flybar for rotor control. Building off that success, they next introduced this TriStar R/C helicopter. It was smaller than the Hughes 300 and modeled after the RotorWay Scorpion homebuilt helicopter that was all the rage in the 1970s and 80s. Du−Bro also offered scale Hughes 500 and Enstrom fuselages for it.

See also my personal Du−Bro Tri−Star helicopter photos. RCM published a product review of the du−Bro Tri−Star helicopter in the May 1975 issue.

Du-Bro Tri-Star R/C Helicopter

Du-Bro Tri-Star R/C Helicopter Build & Review, December 1975 RC Modeler - Airplanes and RocketsWhen Du-Bro introduced the Tri-Star, it entered a market ready for a lower priced helicopter. When I received my Tri-Star kit, I was very enthused with the simplicity of the construction. Everything was bolted together with 6-32 x 3/8" and 6-32 x 1/4" socket head bolts and lock washers. The Tri-Star went together in a minimum of time even when I did not have any instructions to go by.

Let me explain here that I am an experienced helicopter builder and flyer. I also had been to the Du-Bro factory and previewed the original Tri-Star. While at the factory I had the opportunity to fly the Tri-Star and to disassemble and re-assemble it. I received one of the prototypes before the kit was released to the public. This is the reason for my kit not having any instructions with it.

Tri-Star Enstrom Fuselage - Airplanes and Rockets

Tri-Star Enstrom fuselage.

Grady Howard flies the Tri-Star without any fuselage - Airplanes and Rockets

Grady Howard flies the Tri-Star without any fuselage - the best way to learn to fly. Note flag on transmitter -windy and gusty.

The Scorpion version - Airplanes and Rockets

The Scorpion version.

Enstrom configuration requires 2 oz. additional weight in the nose - Airplanes and Rockets

The Enstrom configuration requires 2 oz. additional weight in the nose. All flying photos taken within 30 minutes from the first bare Tri-Star shot.

Tri-Star crutch with skid braces - Airplanes and Rockets

The basic Tri-Star crutch with skid braces, skids, K & B-Lee .40 with Perry pump and carburetor; main gears, radio frame, and main rotor shaft installed.

Close-up view of cylinder head side with heat shield in place - Airplanes and Rockets

Close-up view of cylinder head side with heat shield in place.

Opposite side of frame prior to tank installation - Airplanes and Rockets

Opposite side of frame prior to tank installation.

Semco super expansion muffler installed - Airplanes and Rockets

Semco super expansion muffler installed.

Fuel tank & heat sink installed - Airplanes and Rockets

Fuel tank in place (left). Heat sink is now installed (right).

Close-up of method of installing heat sink - Airplanes and Rockets

Close-up of method of installing heat sink.

Close-up view of gear mesh - Airplanes and Rockets

Close-up view of gear mesh. Note conventional aircraft spinner extension added to small gear to allow direct application of electric starter if desired. A small spinner could also be added, if desired.

 - Airplanes and Rockets

Tail boom and completed drive shaft. Boom must be cut to correct length.

Close-up of end of drive shaft - Airplanes and Rockets

Close-up of end of drive shaft.

Nylon bearing installation - Airplanes and Rockets

Nylon bearing installation. Stabil-It Express used to secure tubing.

Completed tail rotor mechanism - Airplanes and Rockets

Completed tail rotor mechanism.

steel brace for added support - Airplanes and Rockets

An aluminum strap is added from the base of the front skid to the front of the steel brace for added support.

Radio equipment installed - Airplanes and Rockets

The radio equipment installed. Receiver and battery pack wrapped in foam in plastic radio box .

The completed Tri-Star - Airplanes and Rockets

The completed Tri-Star. You can learn to fly it in this mode or you can add the Scorpion fuselage. Enstrom and Hughes 500 bodies also available.  

After a couple of phone calls to Dave Gray at the Du-Bro factory, I had the Tri-Star ready to fly. There were only a few minor things that needed to be cleared up before I could finish the 'copter. My first impression on that first flight was that there was something extremely wrong with my set-up because the tail was extremely sensitive to tail rotor control.

After talking to Dave Gray again, I found out that this was to be expected as I was accustomed to flying a Shark that is heavier and slower to respond.

Back to the backyard again and, this time, I tried to be a little slower on the sticks. This helped to calm the little machine down some. However, to keep the Tri-Star from being really hard to fly, it is very important to get it trimmed out as quickly as possible for a "hands-off" condition. Let me inject here and now, this helicopter is going to be a handful for the rank novice and beginner helicopter flyer! The more experienced flyer can handle the machine and really have a ball with the fast maneuverability and quick response of the Tri-Star.

The toughness of the Tri-Star is really something! I had a flame out at approximately 200 ft. and in one hour I was back in the air flying. l did not have to replace anything at all. I only had to straighten out the bent metal and re-set the rotor head and blades. My machine weighed 7 lbs. ready to fly and the OS Max .40 provided plenty of power.

After the Tri-Star was released I asked for, and subsequently received, a set of the instructions and the exploded views that accompanied the booklet. After reading the booklet and examining the views, I could see the problems that I had heard about from other owners of the Tri-Star. The exploded views are very artistic but leave a lot to be desired in building information. There were some parts views that were backwards and some that were omitted. After talking to Dewey Broberg of Du-Bro about this problem with the plans, it was established that there would be an addition to the original plans using photos to help in the building. This should be of great help to those building the Tri-Star for their first helicopter.

There were several problems and weak points that began to show up after several hours of flying time on the Tri-Star. The most noticeable problem was that the fan would come loose from the arbor to which it was staked (or pinged). I tried correcting this by using silver solder but this did not hold longer than 3 flights. I then drilled two 1/16" holes 180° apart through the fan and the arbor that it was on. The next step was to put two pieces of 1/16" music wire, cut to length, through the holes and brad the ends over. This has worked well with the fan pinned to the arbor.

The next, and more serious problem, was the small gear on the engine would wear out and break off teeth. I went through three gears before I found that I was not getting a good gear mesh and alignment. It seems that the gears had a slight burr on the teeth and, when setting them up with a slight amount of back lash, as specified in the instructions, then after running, the burr would be gone and the gears then had too much back lash. This allowed the small gear to slam into the larger clutch gear on each stroke of the engine, thus causing breaking of teeth and total destruction of the gear. Again, this problem bas been discussed with the Du-Bro factory and they have now started to harden the gears, and this seems to take care of this problem.

The servo mounting frame that is hanging out front is very susceptible to bending down on hard landings. I have added a piece of 1/2" x 1/8" aluminum strip from the front of the frame back to the main frame where the landing gear struts are fastened. I then fastened the strap under one of the landing gear 6-32 bolts. This, then, holds the frame rigid and there is less vibration on the fuselage. I don't know if this is going to be incorporated into the future kits, ·but it is a big help in giving the machine a stronger frame. The tail rotor drive shaft has two bushings on it that must be oiled or they will bind on the aluminum and cause excessive drag and a terrifically loud noise.

I have now flown the Tri-Star in all kinds of wind conditions and even inside. I still have some trouble with the sensitivity of the tail rotor when coming in from altitude to a landing. This, I believe, is due entirely to the fact that the Tri-Star is a little helicopter and most small helicopters respond in this fashion. This is the same with little airplanes compared to big airplanes; the big ones usually handle better and are generally easier to fly.

For those who are shopping for price and have lots of time to practice, then you will like the Tri-Star. If you want a machine that will be easier to fly and more stable even in wind, then go to a larger, heavier helicopter and leave the Tri-Star to those who really want a challenge.

I personally enjoy the size and quickness of the Tri-Star and can really impress the crowd with fast low level figure 8 is with 90° banked turns. I have also looped the Tri-Star without the body on it. You must get it very high (300 ft. or more) and dive for about 150 ft. before easing back on the stick. As the helicopter gets in the vertical position, then you must pull full back and then watch it fall a long way. If you have had sufficient altitude then the chopper will come out the bottom. If not, then you must start repairing.

With the optional fuselages that are available, the Tri-Star can be a different helicopter each day for more fun and enjoyment. The Enstrom fuselage that I have in addition to the Scorpion fuselage, seems to slow down the speed of the tail somewhat and the forward flight speed doesn't seem to be affected. With the Enstrom fuselage on the Tri-Star, I can keep my orientation better because of the mass that the body affords. For flying the Scorpion body only, a 1/32" plywood fin in front of the tail skid helps the tail to "weathervane."

After the learning phase. is over (is it ever?) then I would suggest one of the larger fuselages, if for nothing more than the visibility factor.

Overall I feel the Du-Bro Tri-Star is a fine small helicopter for the more experienced helicopter flyer, but I feel that it is definitely not a beginner's helicopter.

Plastic box painted with K & B Superpoxy - Airplanes and Rockets

The top of the radio box is secured with a rubber band. Plastic box painted with K & B Superpoxy.

Linkage attachment from servos to cyclic bellcranks - Airplanes and Rockets

Note linkage attachment from servos to cyclic bellcranks. One was shown reversed on our plans.

Swashplate and scissors installed - Airplanes and Rockets

The swashplate and scissors installed. Make sure there is no binding in latter.

tail fin added to aid in weathervaning - Airplanes and Rockets

1/32" ply tail fin added to aid in weathervaning.

Tail rotor gear box and blades installed - Airplanes and Rockets

Tail rotor gear box and blades installed.

Basic head assembly with all bearings in place - Airplanes and Rockets

Basic head assembly with all bearings in place.

Swash plate assembly - Airplanes and Rockets

Photos above and below show both sides of the completed swash plate and main rotor assembly.

Main rotor assembly - Airplanes and Rockets


Scorpion body shell halves joined together with Zap - Airplanes and Rockets

The Scorpion body shell halves joined together with Zap. Note reinforcing piece on Inside bottom. DJ's wide trim sheets and. tape used for co/or trim.



Posted June 1, 2019

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